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Stephen D. Eckermann, Dave Broutman, Jun Ma, James D. Doyle, Pierre-Dominique Pautet, Michael J. Taylor, Katrina Bossert, Bifford P. Williams, David C. Fritts, and Ronald B. Smith

DVAR) DA algorithm. Hogan et al. (2014) provide a detailed description of the key model and DA components. In common with other operational DA systems, the current operational NAVGEM has a rigid upper boundary at 0.04 hPa ( z ~ 70 km: Hogan et al. 2014 ). For the DEEPWAVE reanalysis, the forecast model was reconfigured from 60 to 74 levels (L74) with a new upper boundary at 6 × 10 −5 hPa ( z ~ 115 km), then augmented with a range of additional physical parameterizations needed to model the

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Ronald B. Smith and Christopher G. Kruse

the wave field sees this finescale terrain. Even if it did, those short-wavelength waves would be nonhydrostatic and carry little momentum flux ( Smith and Kruse 2017 ). 4. The WRF wave drag dataset for New Zealand a. Data quality The observational basis for the current study is a continuous full-physics WRF Model simulation of airflow over New Zealand, done for the DEEPWAVE project from June through August 2014. The mesoscale simulation was carried out with 6-km resolution with boundary

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Christopher G. Kruse and Ronald B. Smith

. 1. Examples of (a) full pressure ( p ), (b) deplaned pressure ( ), (c) low-passed deplaned pressure ( ), and (d) high-passed deplaned pressure or perturbation pressure ( ) from a realistic 2-km WRF simulation. A cutoff length scale of L = 400 km was used. These analyses are valid at 1800 UTC 24 Jun 2014 at 4-km MSL. While edge artifact amplitude is reduced via deplaning, edge artifacts are not eliminated (e.g., Fig. 1d ). Edge artifacts decay away from the boundaries with a decay length scale

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Ronald B. Smith, Alison D. Nugent, Christopher G. Kruse, David C. Fritts, James D. Doyle, Steven D. Eckermann, Michael J. Taylor, Andreas Dörnbrack, M. Uddstrom, William Cooper, Pavel Romashkin, Jorgen Jensen, and Stuart Beaton

current state of knowledge of gravity waves fluxes around the world is nicely reviewed by Geller at al. (2013) . They emphasize that satellites and global models are unable to resolve the short wavelength components of the gravity wave spectrum. In addition, wave parameterization schemes are oversimplified and differ from model to model. As a result, there are significant differences and uncertainties in regional wave momentum flux (MF) estimates. In the Southern Hemisphere winter, for example, the

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Christopher G. Kruse, Ronald B. Smith, and Stephen D. Eckermann

little to nearly half of tropopause-level tropical upwelling among model members. Surprisingly, despite variable GWD contributions, the circulation strength was found to be relatively constant, implying changes in planetary wave driving compensate variations in GW forcing (e.g., Cohen et al. 2013 ) and that the mean transport circulation alone may not strongly constrain GWD parameterizations. A current common problem in chemistry–climate models is that the Southern Hemisphere pole is too cold in the

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Christopher G. Kruse and Ronald B. Smith

use of periodic lateral boundary conditions, 2D flow, and no planetary vorticity . These idealizations limit the ambient flow response to MWD to deceleration, preventing MWD from being balanced by a pressure gradient or Coriolis force in a barrier jet–like response. The total (nondissipative plus dissipative) MW momentum deposition and ambient flow decelerations are trivially diagnosed in the MW–ambient flow coupled WRF solutions, as the model numerics time integrate the total momentum deposition

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Ronald B. Smith and Christopher G. Kruse

analysis and area averaging superior to the narrow leg averages from aircraft. Numerical simulation allows us to include several fluid dynamical aspects that are missing from the theory in section 3 , especially unsteadiness, nonlinearity, variable wind and stability with height, boundary layer dynamics, and terrain three-dimensionality. Five 2-km-resolution full-physics Weather Research and Forecasting (WRF) Model simulations of 3D time-dependent airflow over New Zealand ( Table 3 ) were recently

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